OT - Foam over existing duct insulation...?
 

Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

Sincere thanks,
--
Kenneth

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OT - Foam over existing duct insulation...?
 

"Kenneth" wrote in message

Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

Are the ducts to be coated in a layer foam or entirely
embedded? If the former, find out how well the foam
will adhere to the existing insulation - you don't
want it falling off over time.

OT - Foam over existing duct insulation...?
 

On Thu, 20 Mar 2008 08:33:42 -0400, "Greg Neill"
wrote:

"Kenneth" wrote in message

Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

Are the ducts to be coated in a layer foam or entirely
embedded? If the former, find out how well the foam
will adhere to the existing insulation - you don't
want it falling off over time.

Hi Greg,

Thanks for the response...

The ducts run along the floor and are rectangular in cross
section. As a result, the foam would be sprayed up one side,
over the top, down the other side, and then down onto the
floor for a few inches on both sides.

Any further thoughts?

All the best,
--
Kenneth

If you email... Please remove the "SPAMLESS."

OT - Foam over existing duct insulation...?
 

"Kenneth" wrote in message

On Thu, 20 Mar 2008 08:33:42 -0400, "Greg Neill"
wrote:

Are the ducts to be coated in a layer foam or entirely
embedded? If the former, find out how well the foam
will adhere to the existing insulation - you don't
want it falling off over time.

Hi Greg,

Thanks for the response...

The ducts run along the floor and are rectangular in cross
section. As a result, the foam would be sprayed up one side,
over the top, down the other side, and then down onto the
floor for a few inches on both sides.

Any further thoughts?

If the foam will adhere to the existing insulation,
and that insulation is not going to fall off of the
ducts, then I'd leave it in place. It'll add a bit
of insulating value. Make sure that the duct ends
where the insulation terminates are sealed; an air
gap between the exhisting insulation and the duct
can form a path for conditioned air to leak out at
the terminations if the duct seams are not air tight.

OT - Foam over existing duct insulation...?
 

On Thu, 20 Mar 2008 09:44:57 -0400, "Greg Neill"
wrote:

"Kenneth" wrote in message

On Thu, 20 Mar 2008 08:33:42 -0400, "Greg Neill"
wrote:

Are the ducts to be coated in a layer foam or entirely
embedded? If the former, find out how well the foam
will adhere to the existing insulation - you don't
want it falling off over time.

Hi Greg,

Thanks for the response...

The ducts run along the floor and are rectangular in cross
section. As a result, the foam would be sprayed up one side,
over the top, down the other side, and then down onto the
floor for a few inches on both sides.

Any further thoughts?

If the foam will adhere to the existing insulation,
and that insulation is not going to fall off of the
ducts, then I'd leave it in place. It'll add a bit
of insulating value. Make sure that the duct ends
where the insulation terminates are sealed; an air
gap between the exhisting insulation and the duct
can form a path for conditioned air to leak out at
the terminations if the duct seams are not air tight.

Hi Doug,

I appreciate your suggestions...

Yes, the present insulation is firmly attached everywhere,
and as I am collecting information about this, it does
appear that I will go in the direction of insulating over
it, as you have suggested.

All the best,
--
Kenneth

If you email... Please remove the "SPAMLESS."

OT - Foam over existing duct insulation...?
 

On Mar 20, 4:06*am, Kenneth wrote:

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

The ducts aren't just insulated, they're muffled by the quilted
stuff. You want to keep it.

Because adhesion on the ducts would make (for instance)
foam removal destructive to ducting, I'd staple a layer of
paper (maybe Tyvek housewrap) over the existing ducts,
so the foam wouldn't penetrate and adhere. Tyvek isn't
going to chemically interact with the foam.

OT - Foam over existing duct insulation...?
 

The "shiny" quilted stuff, probably mylar with a mirror finish, should serve
as a radiant barrier and add to the efficiency.
Respectfully,
Ron Moore

"Kenneth" wrote in message
...


Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

Sincere thanks,
--
Kenneth

If you email... Please remove the "SPAMLESS."

OT - Foam over existing duct insulation...?
 

On Thu, 20 Mar 2008 18:50:30 -0500, "Ron Moore"
wrote:


"Kenneth" wrote in message
.. .


Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

Sincere thanks,
--
Kenneth

If you email... Please remove the "SPAMLESS."


The "shiny" quilted stuff, probably mylar with a mirror finish, should serve
as a radiant barrier and add to the efficiency.
Respectfully,
Ron Moore

Hi Ron,

I want to be certain that I am interpreting your comment
correctly...

Am I correct to assume that you are suggesting that its
reflective properties would be of benefit, and therefore
should be left in place under the foam?

Sincere thanks,
--
Kenneth

If you email... Please remove the "SPAMLESS."

OT - Foam over existing duct insulation...?
 

That's my thought on it. We just did a warehouse to office/residence
conversion and made extensive use of foil-backed materials. We're very
pleased with the efficiency we've achieved. That 10,000' is costing less
per month to heat then an older 1500' office that has not been "cocooned"
in this manner.
Respectfully,
Ron Moore

"

The "shiny" quilted stuff, probably mylar with a mirror finish, should
serve
as a radiant barrier and add to the efficiency.
Respectfully,
Ron Moore

Hi Ron,

I want to be certain that I am interpreting your comment
correctly...

Am I correct to assume that you are suggesting that its
reflective properties would be of benefit, and therefore
should be left in place under the foam?

Sincere thanks,
--
Kenneth

If you email... Please remove the "SPAMLESS."